set6: challenge44: completed

2 files changed, 18 insertions, 0 deletions

diff --git a/lib/lib6.c b/lib/lib6.c
index 7239228..ef0db85 100644
--- a/lib/lib6.c
+++ b/lib/lib6.c
@@ -209,3 +209,18 @@ void dsa_recover_x_from_known_k(struct dsa_public_params *pub, BIGNUM *k,
 	BN_mod_sub(priv->private, priv->private, mess_hash, pub->q, ctx);
 	BN_mod_mul(priv->private, priv->private, r_1, pub->q, ctx);
 }
+
+void dsa_recover_k_from_repeated_nonce(BIGNUM *mess1_hash, BIGNUM *mess2_hash,
+		BIGNUM *s1, BIGNUM *s2, struct dsa_public_params *pub,
+		struct dsa_per_user_param *priv, BIGNUM *k)
+{
+
+	BIGNUM *diff1 = BN_new();
+
+	BN_mod_sub(diff1, mess1_hash, mess2_hash, pub->q, ctx);
+	BN_mod_sub(k, s1, s2, pub->q, ctx);
+	BN_mod_inverse(k, k, pub->q, ctx);
+	BN_mod_mul(k, k, diff1, pub->q, ctx);
+	printf("recoverd k is: \n");
+	BN_print(out, k);
+}
diff --git a/lib/lib6.h b/lib/lib6.h
index 88fc530..dbd435b 100644
--- a/lib/lib6.h
+++ b/lib/lib6.h
@@ -37,4 +37,7 @@ int dsa_verify(char *mess, struct dsa_public_params *pub, struct dsa_per_user_pa
 		*priv);
 void dsa_recover_x_from_known_k(struct dsa_public_params *pub, BIGNUM *k,
 		struct dsa_per_user_param *priv, BIGNUM *mess_hash);
+void dsa_recover_k_from_repeated_nonce(BIGNUM *mess1_hash, BIGNUM *mess2_hash,
+		BIGNUM *s1, BIGNUM *s2, struct dsa_public_params *pub,
+		struct dsa_per_user_param *priv, BIGNUM *k);
 #endif /* __LIB_6_H__ */